1. Field of the Invention
The present invention is directed to a method and system for controlling a gas temperature in a plasma processing environment.
2. Discussion of the Background
Plasma reactors are being constructed with increasingly tight process controls. Plasma processes involve dissociating the molecules in the gas within the process chamber using an RF electric field. Dissociation within the plasma creates positively charged ions, free electrons, and neutrals. These particles interact with the wafer and with each other. These interactions are governed by chemical principles. One dominant factor governing these reactions is temperature. Temperature control systems exist to regulate the temperature of wafers when they are on a wafer chuck in a reactor being etched.
U.S. Pat. No. 5,653,808, entitled xe2x80x9cGas injection system for CVD reactors,xe2x80x9d describes a CVD reactor that includes separate reaction and pressure chambers, where the reaction chamber is contained within and isolates reactant gases from the pressure chamber. The reactor also includes a gas injection system that injects process gas(es) (e.g., hydrogen) into the reaction chamber in a somewhat vertical direction through a bottom surface of the reaction chamber.
The flow of the gas is intermediate the flow of the process gas(es) and a surface of the reaction chamber, thereby re-directing the process gas flow parallel to the top surface of a wafer therein. In this manner, the reaction chamber does not require a long entry length for the process gas(es).
U.S. Pat. No. 5,911,834, entitled xe2x80x9cGas delivery systemxe2x80x9d and assigned to Applied Materials Inc. (Santa Clara, Calif.), describes a method and apparatus for delivering at least one process gas and at least one cleaning gas into at least one processing region. The gas distribution system includes a gas inlet and a gas conduit, each disposed to deliver at least one gas into the chamber via a desired diffusing passage. Also, a gas delivery method and apparatus for splitting a gas feed into multiple feed lines is provided having a gas filter disposed upstream from a splitting coupling disposed in the line.
U.S. Pat. No. 6,030,456, entitled xe2x80x9cInstallation to supply gasxe2x80x9d and assigned to Winbond Electronics Corp. (Hsinchu, TW), describes an adjustable gas supply in a reaction chamber according to the conditions in the reaction chamber. The installation comprises sensors, a gas-supplying panel and a driving device. The sensors are located in the reaction chamber to sense the conditions in the reaction chamber. The gas-supplying panel has a plurality of asymmetrically located apertures and gas is supplied through these apertures. The driving device, coupled to the sensors and the gas-supplying panel, drives the gas-supplying panel to respond to the conditions sensed by the sensors, in which the gas-supplying panel can adjust the positions of the gas supplied through the apertures.
U.S. Pat. No. 6,068,703, entitled xe2x80x9cGas mixing apparatus and methodxe2x80x9d and assigned to Applied Materials, Inc. (Santa Clara, Calif.), describes apparatuses, systems, and methods related to the manufacture of integrated circuits. Specifically, embodiments include apparatus designed to provide mixture for gases used in a semiconductor processing system. In one embodiment, the gas mixing apparatus includes a gas mixer housing having a gas inlet, a fluid flow channel, and a gas outlet. The fluid flow channel is fluidly coupled to a plurality of gas sources. The majority of the gas mixture occurs in the fluid flow channel which includes one or more fluid separators for separating the gas into plural gas portions and one or more fluid collectors for allowing the plural gas portions to collide with each other to mix the gas portions.
U.S. Pat. No. 6,071,349, entitled xe2x80x9cGas supplying apparatus and vapor-phase growth plantxe2x80x9d and assigned to Shin-Etsu Handotai Co. Ltd. (Tokyo, JP), describes a vapor-phase growth plant which has a dopant gas supplying apparatus including plural dopant gas supplying containers, and a multiple stage gas flow subsystem with plural dopant gas supply conduits therein. The dopant gas supply conduits form a tournament-style network with a plurality of confluences on which the dopant gas supply conduits are united and the gas flows therein are merged for subjection to mixing which results in a decreasing number of dopant gas supply conduits as the dopant gas flows proceed in the multiple stage gas flow subsystem.
The above discussed patents solve some temperature related problems, however, the temperatures of gases entering the process chamber during the etching process are not controlled.
It is an object of the present invention to extend the range of etching process recipes by providing control of the temperatures of the gases. Generally the present invention is directed to a method of controlling the temperature of at least one gas prior to the gas entering a process chamber. Temperature controllers can also be used to vary gas temperatures at different spatial regions of a showerhead assembly (either an individual gas species or mixed gas species).
According to one embodiment, an in-line heat exchanger alters (i.e., increases or decreases) the temperature of passing gas species (either high- or low-density) prior to entering a process chamber, temperature change of the gases is measured by determining a temperature of the gas both upon entrance into the in-line heat exchanger assembly and upon exit. This enables tracking of the operation of the system configuration by a gas temperature control system and prediction of what will happen in the process chamber. Depending on the desired reactant gas mixture, gas species can be heated or cooled to different temperatures before being mixed and subsequently dispersed into a process chamber.
In at least one embodiment, the present invention increases at least one performance characteristic (e.g., etch rate, uniformity, selectivity, ease of chamber cleaning, and various plasma properties).